Method for forging plate and method for manufacturing a liquid ejection head

ABSTRACT

There is disclosed a punch for forging a metallic plate member. A first die is adapted to be opposed to a first face of the plate member. A second die is adapted to be opposed to a second face of the plate member. A plurality of first projections are provided on the first die and arranged in a first direction with a fixed pitch. Each of the first projections is elongated in a second direction perpendicular to the first direction. A plurality of second projections are provided on the second die and arranged in the first direction with the fixed pitch. Each of the second projections is elongated in the second direction and provided with a concave portion extending in the second direction at a distal end portion thereof. The plate member is sandwiched between the first die and the second die so that the first projections and the second projections are cut into the plate member in a third direction orthogonal to the first direction and the second direction, to perform a first forging work.

CROSS REFERENCE

This is a divisional of application Ser. No. 10/644,091 filed Aug. 20,2003 now U.S. Pat. No. 6,997,027. The entire disclosure of the priorapplication, application Ser. No. 10/644,091 is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

The present invention relates to a forging punch to be used formanufacturing a component such as a liquid ejection head. The presentinvention also relates to a minute forging method and a method ofmanufacturing a liquid ejection head using the same.

Forging work is used in various fields of products. For example, it isthought that a pressure generating chamber of a liquid ejection head ismolded by forging metal material. The liquid ejection head ejectspressurized liquid from a nozzle orifice as a liquid droplet, and theheads for various liquids have been known. An ink jet recording head isrepresentative of the liquid ejection head. Here, the related art willbe described with the ink jet recording head as an example.

An ink jet recording head (hereinafter, referred to as “recording head”)used as an example of a liquid ejection head is provided with aplurality of series of flow paths reaching nozzle orifices from a commonink reservoir via pressure generating chambers in correspondence withthe orifices. Further, the respective pressure generating chambers needto form by a fine pitch in correspondence with a recording density tomeet a request of downsizing. Therefore, a wall thickness of a partitionwall for partitioning contiguous ones of the pressure generatingchambers is extremely thinned. Further, an ink supply port forcommunicating the pressure generating chamber and the common inkreservoir is more narrowed than the pressure generating chamber in aflow path width thereof in order to use ink pressure at inside of thepressure generating chamber efficiently for ejection of ink drops.

According to a related-art recording head, a silicon substrate ispreferably used in view of fabricating the pressure generating chamberand the ink supply port having such small-sized shapes with excellentdimensional accuracy. That is, a crystal surface is exposed byanisotropic etching of silicon and the pressure generating chamber orthe ink supply port is formed to partition by the crystal surface.

Further, a nozzle plate formed with the nozzle orifice is fabricated bya metal board from a request of workability or the like. Further, adiaphragm portion for changing a volume of the pressure generatingchamber is formed into an elastic plate. The elastic plate is of atwo-layer structure constituted by pasting together a resin film onto asupporting plate made of a metal and is fabricated by removing a portionof the supporting plate in correspondence with the pressure generatingchamber. Such a structure is disclosed in Japanese Patent PublicationNo. 2000-263799A, for example.

Since the thickness of the partition wall is extremely thinned, it ishard to accurately obtain the recessed shape of the pressure generatingchamber to uniformly set the liquid containing volume thereof. Since therecessed shape is generally elongated in many cases, the length of thepartition wall is accordingly increased. For this reason, it isimportant that the partition wall is to be accurately fabricated over anentire length in order to uniformly maintain the liquid containingvolume. In particular, it is important that the height of the partitionwall is sufficiently maintained in a manufacturing stage in order toobtain proper recessed shapes of adjacent pressure generating chambers.

Meanwhile, according to the above-described related-art recording head,since a difference between linear expansion rates of silicon and themetal is large, in pasting together respective members of the siliconboard, the nozzle plate and the elastic plate, it is necessary to adherethe respective members by taking a long time period under relatively lowtemperature. Therefore, enhancement of productivity is difficult toachieve to bring about a factor of increasing fabrication cost.Therefore, there has been tried to form the pressure generating chamberat the board made of the metal by plastic working, however, the workingis difficult since the pressure generating chamber is extremely smalland the flow path width of the ink supply port needs to be narrower thanthe pressure generating chamber to thereby pose a problem thatimprovement of production efficiency is difficult to achieve.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to precisely form a partitionwall to obtain recessed shapes of adjacent pressure generating chamberswith high precision.

In order to achieve the above object, according to the invention, thereis provided a punch for forging a metallic plate member, comprising:

a first die, adapted to be opposed to a first face of the plate member;

a second die, adapted to be opposed to a second face of the platemember;

a plurality of first projections, provided on the first die and arrangedin a first direction with a fixed pitch, each of the first projectionsbeing elongated in a second direction perpendicular to the firstdirection; and

a plurality of second projections, provided on the second die andarranged in the first direction with the fixed pitch, each of the secondprojections being elongated in the second direction and provided with aconcave portion extending in the second direction at a distal endportion thereof,

wherein the plate member is sandwiched between the first die and thesecond die so that the first projections and the second projections arecut into the plate member in a third direction orthogonal to the firstdirection and the second direction, to perform a first forging work.

The material in the plate member is pressurized between both of the diesare caused to flow to be pushed into the gaps between the firstprojections. Incidentally, at portions on both sides of the concaveportion, an interval between both of the dies is smaller than theportion where the concave portion is provide, so that an amount of thepressurization of the material is increased. The material thuspressurized is caused to flow to be pushed out in the second directionand the material is moved toward the concave portion at which theinterval between both of the dies becomes large so that an amount of thepressurization becomes small. In other words, the concave portion servesto provide a place into which the material escapes.

Accordingly, the flow of the material into the gaps is positivelycarried out over the whole region in the second direction of the gaps.Moreover, since the projections are arranged at the fixed pitch, theflow of the material in the first direction is made uniform for both thedirection of the flow and the amount of the flow.

In a case where the material flowing in the gaps become partition wallsof the recesses formed by the first projections, the shape of therecesses can be obtained accurately. Furthermore, since the processingcan be carried out to cause the volume of each recess to be uniform, ina case where the pressure generating chamber for the liquid ejectionhead is to be formed, for example, the ejection property of the liquidejection head is stabilized.

Preferably, the second die is arranged such that each of the secondprojections is opposed to a gap defined between adjacent ones of thefirst projections. In this case, the height of the second projectionscan be efficiently used to cause the material to flow into the gapsbetween the first projections.

Alternatively, the second die may be arranged such that each of thesecond projections is opposed to an associated one of the firstprojections. In this case, the pressurizing force can be maximizedbetween the first and second projections to promote the material flowinto the gaps between the first projections.

Preferably, the concave portion is arranged at a center portion of eachof the second projections with regard to the second direction. In thiscase, the amount of material flow from both sides of the concave portioncan be made equal.

Preferably, the concave portion has an arcuate shape when viewed fromthe first direction. In this case, the material can be smoothly flowninto the concave portion.

Alternatively, the concave portion may be, formed with a plurality offlat faces.

Alternatively, a convex portion is formed on a bottom portion of theconcave portion. In this case, it is prevented the stress fromconcentrating the bottom portion, which otherwise cause to generate acrack at the bottom portion.

Here, it is preferable that the convex portion has a height such anextent that a plurality of concave portions are substantially defined bythe convex portion. In this case, a plurality of portions in which theamount of the pressurization is large and small are provided alternatelyso that the amount of the material flowing to the gaps can be furthermade uniform in the second direction.

In order to the same advantages, instead of the convex portion, a recessportion may be formed at a bottom portion of the concave portion.

Preferably, a length of the concave portion in the second direction is ⅔or less of a length of each of the second projections in the seconddirection. In this case, the amount of the flow of the material in thesecond direction and the size of the concave portion for receiving thesame amount can be balanced properly with a pressurizing stroke. Thus,the flow of the material into the gaps is optimized.

In order to attain the same advantage, it is preferable that a ratio ofa depth of the concave portion with respect to a length of the concaveportion in the second direction falls within a range of 0.05 to 0.3.

In order to attain the same advantage, a ratio of a depth of the concaveportion with respect to a height of each of the second projections fallswithin a range of 0.5 to 1.

Preferably, at least the concave portion of each of the secondprojections is finished with either mirror finishing or chromiumplating. In this case, the material flow into the gaps between the firstprojections can be promoted.

Preferably, each of the second projections has a wedge-shaped crosssection when viewed from the second direction. In this case, the secondprojections can be surely cut into the plate member.

Here, it is preferable that a distal end angle of the wedge-shaped crosssection is 90 degrees or less.

Preferably, the fixed pitch is 0.3 mm or less. For forming such a minutestructure, an anisotropic etching method is generally employed. Sincesuch a method requires a large processing man-hour, it isdisadvantageous in respect of the manufacturing cost. However, theforging punch of the invention can be applied to obtain such a minutestructure to considerably reduce the manufacturing cost.

Preferably, the punch further comprises a third die, adapted to beopposed to the second face of the plate member on which the firstforging work has been performed. The plate member is sandwiched betweenthe first die and the third die so that only the first projections arecut into the plate member in the third direction, to perform a secondforging work.

Here, it is preferable that: the third die is formed with a pair ofthird projections arranged in the second direction and elongated in thefirst direction so as to define a groove therebetween; and each of thethird projections has a flat distal end face. In this case, since thematerial flown into the gaps between the first projections is furtherpressurized by the flat faces, the height of the material to bepartition walls are made uniform entirely in the first and seconddirections.

It is also preferable that the concave portion in the second die and thegroove in the third die are placed at a same position with respect tothe plate member in connection with the second direction. In this case,since the protrusion formed by the concave portion on the second face ofthe plate member is received by the groove, the material at theprotrusion never flows into the gaps between the first projections sothat it contributes the uniformization of the partition wall height.

It is also preferable that sloped flat faces continued from the flatdistal end face are provided at both end portions in the first directionof each of the third projections, such that a portion closer to an endin the first direction of each of the third projections is moreseparated from the first die.

The material flows in the first direction little by little from thecentral part toward the both ends so that the vicinity of the ends ofthe plate member are made thick due to the accumulation of the plasticflow. With the above configuration, since the thick portions arepressurized by the sloped faces which are lowered, the material in thethick portions can be prevented from excessively flowing into the gaps.Accordingly, the amount of the flow of the material can be as uniform aspossible in all the gaps.

It is also preferable that a depth of the groove falls within a range of0.05 mm to 0.15 mm, and a length in the second direction of the groovefalls within a range of 0.5 mm to 1 mm. In this case, the amount of theflow of the material in the second direction and the size of the groovefor receiving the same amount can be balanced properly with apressurizing stroke. Thus, the flow of the material into the gaps isoptimized.

Preferably, the second die and the third die are arranged such that thefirst forging work and the second forging work are performed in aprogressive manner. In this case, the positioning operation of theworked object in each stage can be precisely performed so that themolding accuracy is enhanced, so that the forging works can beefficiently conducted.

According to the invention, there is also provided a forging apparatuscomprising the above forging punch.

According to the invention, there is also provided a method of forging ametallic plate member, comprising steps of:

providing a first die, in which a plurality of first projections arearranged in a first direction with a fixed pitch, each of the firstprojections being elongated in a second direction perpendicular to thefirst direction;

providing a second die, in which a plurality of second projections arearranged in the first direction with the fixed pitch, each of the secondprojections being elongated in the second direction and provided with aconcave portion extending in the second direction at a distal endportion thereof;

providing a third die, in which a pair of third projections arranged inthe second direction and elongated in the first direction so as todefine a groove therebetween, each of the third projections having aflat distal end face;

opposing the first die to a first face of the plate member whileopposing the second die to a second face of the plate member;

performing a first forging work by sandwiching the plate member with thefirst die and the second die in a third direction orthogonal to thefirst direction and the second direction, so as to generate a plasticflow of a material in the plate member into gaps defined between thefirst projections while generating a plastic flow of the material intothe concave portion of each of the second projection;

opposing the third die to the second face of the plate member, after thefirst forging work; and

performing a second forging work, by sandwiching the plate member withthe first die and the third die in the third direction, such that theflat distal end face of each of the third projections generates aplastic flow of the material into the gaps between the firstprojections, while a protrusion formed on the plate member by theconcave portion is received by the groove,

wherein a plurality of recesses formed by the first projections arepartitioned by partition walls formed by the material flown into thegaps between the first projections.

According to the invention, there is also provide a method ofmanufacturing a liquid ejection head, using the above forging method,comprising steps of:

forming a through hole in each of the recesses so as to communicate eachof the recesses with the second face of the plate member;

joining a sealing plate onto the first face of the plate member so as toseal the recesses;

providing a metallic nozzle plate formed with a plurality of nozzles;and

joining the nozzle plate, with an adhesive agent, onto the second faceof the plate member such that each of the nozzles is communicated withan associated one of the recesses via the through hole,

wherein the liquid ejection head is configured such that liquid dropletsare ejected from the nozzles by pressure fluctuation generated in liquidcontained in the recesses.

As described above, the recess portions elongated in the seconddirection and arranged side by side in the first direction are obtainedwith the partition walls finished precisely. The formation requires aless processing man-hour than that in the anisotropic etching method.Furthermore, the processing can be carried out to cause the volume ofeach recess to be uniform. Therefore, the manufacturing method isoptimum for forming the minute pressure generating chambers of theliquid ejection head in which the ejection property is stabilized.

Preferably, a plurality of dents formed by the second projections andremained on the second face of the plate member are used to receiveexcess adhesive agent when the nozzle plate is joined onto the secondface of the plate member.

In this case, the thickness of the adhesive layer is optimized forenhancing a bonding strength between the plate member (chamber formationplate) and the nozzle plate.

Preferably, a height of one of the flat distal end faces of the thirdprojections which is closer to a portion where the through hole is to beformed is lower than the other one of the flat distal end faces. In thiscase, an amount of the material pressed by the one flat face closer tothe through hole is smaller than that of the material pressed by theother flat face, so that a density or hardness of the material closer tothe through hole are lower than those of the other side. Accordingly,the work resistance acting on a punch used for forming of the through isreduced, so that durability of the punch is improved, and this featureis advantageous in improving the working accuracy of the through hole.

According to the invention, there is also provided a liquid ejectionhead manufactured by the above method, wherein a plurality of dents arearranged on the second face of the plate member with the fixed pitch.

Since the pitch of the dents is substantially equal to that of thepressure generating chambers in the first direction, the dents aredistributed at regular spatial intervals on the second face. As aresult, the dents uniformly receives the excessive adhesive agent, thethickness of the adhesive layer is optimized over a broad area, so thatthe bonding strength is increased.

Here, it is preferable that each of the dents is formed in the vicinityof the through hole. In this case, since the excessive adhesive agent isreceived by the dent near the through hole, no adhesive agent overflowsfrom the dent into a passage space of the through hole. Accordingly,there is no chance that air bubbles stay at the locations where theadhesive agent overflows, so that a preferable ink flow is secured.

Preferably, the plate member is comprised of nickel. In this case, thecoefficients of linear expansion of the chamber formation plate, thesealing plate and the nozzle plate constituting the flow path unit arealmost equal to each other. When these members are heated and bonded toeach other, therefore, each of them expands evenly. Consequently, amechanical stress such as a warpage caused by a difference in thecoefficient of expansion is generated with difficulty. As a result, eachmember can be bonded without a hindrance even if a bonding temperatureis set to be high. Even if a piezoelectric vibrator generates heat whenthe recording head is operated and the flow path unit is heated, eachmember constituting the flow path unit expands evenly. For this reason,even if the heating and the cooling are repetitively carried out by theoperation of the recording head and the stop of the operationrespectively, a drawback such as a separation is caused over each memberconstituting the flow path unit with difficulty.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent by describing in detail preferred exemplary embodimentsthereof with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective view of a disassembled ink jet recording headaccording to a first example;

FIG. 2 is a sectional view of the ink jet recording head;

FIGS. 3A and 3B are views for explaining a vibrator unit;

FIG. 4 is a plan view of a chamber formation plate;

FIG. 5A is a view enlarging an X portion in FIG. 4;

FIG. 5B is a sectional view taken along a line A—A of FIG. 5A;

FIG. 5C is a sectional view taken along a line B—B of FIG. 5A;

FIG. 6 is a plan view of an elastic plate;

FIG. 7A is a view enlarging a Y portion of FIG. 6;

FIG. 7B is a sectional view taken along a line C—C of FIG. 7A;

FIGS. 8A and 8B are views for explaining a male die used in forming anelongated recess portion;

FIGS. 9A and 9B are views for explaining a female die used in formingthe elongated recess portion;

FIGS. 10A to 10C are views for explaining a step of forming theelongated recess portion;

FIG. 11 is a perspective view showing a relationship between the maledie and a material to be processed;

FIG. 12A is a perspective view of a preforming female die according toone embodiment of the invention;

FIGS. 12B and 12C are sectional views showing a primary molding;

FIG. 12D is a sectional view taken along a line D—D in FIG. 12C;

FIG. 12E is a modified example of a position of the preforming femaledie;

FIG. 13A is a perspective view of a finishing female die according toone embodiment of the invention;

FIGS. 13B and 13C are sectional views showing a secondary molding;

FIG. 13D is a sectional view taken along a line D—D in FIG. 13C;

FIG. 14A is an enlarged view of one projection in the preforming femaledie;

FIG. 14B is a section view taken along a line B—B in FIG. 14A;

FIG. 14C is a section view taken along a line C—C in FIG. 14A;

FIG. 15 is an enlarged view for explaining dimensions of essential partsof the projection in the preforming female die;

FIG. 16A is an enlarged view of a first modified example of thepreforming female die;

FIG. 16B is an enlarged view of a second modified example of thepreforming female die;

FIG. 17A is an enlarged view of a third modified example of thepreforming female die;

FIG. 17B is an enlarged view of a fourth modified example of thepreforming female die;

FIG. 17C is an enlarged view of a fifth modified example of thepreforming female die;

FIG. 17D is an enlarged view of a sixth modified example of thepreforming female die;

FIG. 17E is an enlarged view of a seventh modified example of thepreforming female die;

FIG. 17F is an enlarged view of an eighth modified example of thepreforming female die;

FIG. 18A is an enlarged view of a first modified example of thefinishing female die;

FIG. 18B is an enlarged view of a second modified example of thefinishing female die;

FIG. 19 is an enlarged view of a third modified example of the finishingfemale die;

FIG. 20A is an enlarged section view showing an essential part of thechamber formation plate;

FIG. 20B is an enlarged plan view of the chamber formation plateobtained by using the preforming female arrangement shown in FIGS. 12Band 12C;

FIG. 20C is an enlarged plan view of the chamber formation plateobtained by using the preforming female arrangement shown in FIGS. 12E;and

FIG. 21 is a sectional view for explaining an ink jet recording headaccording to a second example.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will be described below with reference tothe accompanying drawings. Firstly, the constitution of a liquidejection head will be described.

Since it is preferable to apply the invention to a recording head of anink jet recording apparatus, as an example representative of the liquidejection head, the above recording head is shown in the embodiment.

As shown in FIGS. 1 and 2, a recording head 1 is roughly constituted bya casing 2, a vibrator unit 3 contained at inside of the casing 2, aflow path unit 4 bonded to a front end face of the casing 2, aconnection board 5 arranged onto a rear end face of the casing 2, asupply needle unit 6 attached to the rear end face of the casing 2.

As shown in FIGS. 3A and 3B, the vibrator unit 3 is roughly constitutedby a piezoelectric vibrator group 7, a fixation plate 8 bonded with thepiezoelectric vibrator group 7 and a flexible cable 9 for supplying adrive signal to the piezoelectric vibrator group 7.

The piezoelectric vibrator group 7 is provided with a plurality ofpiezoelectric vibrators 10 formed in a shape of a row. The respectivepiezoelectric vibrators 10 are constituted by a pair of dummy vibrators10 a disposed at both ends of the row and a plurality of drive vibrators10 b arranged between the dummy vibrators 10 a. Further, the respectivedrive vibrators 10 b are cut to divide in a pectinated shape having anextremely slender width of, for example, about 50 μm through 100 μm, sothat 180 pieces are provided.

Further, the dummy vibrator 10 a is provided with a width sufficientlywider than that of the drive vibrator 10 b and is provided with afunction for protecting the drive vibrator 10 b against impact or thelike and a guiding function for positioning the vibrator unit 3 at apredetermined position.

A free end portion of each of the piezoelectric vibrators 10 isprojected to an outer side of a front end face of the fixation plate 8by bonding a fixed end portion thereof onto the fixation plate 8. Thatis, each of the piezoelectric vibrators 10 is supported on the fixationplate 8 in a cantilevered manner. Further, the free end portions of therespective piezoelectric vibrators 10 are constituted by alternatelylaminating piezoelectric bodies and inner electrodes so that extendedand contracted in a longitudinal direction of the elements by applying apotential difference between the electrodes opposed to each other.

The flexible cable 9 is electrically connected to the piezoelectricvibrator 10 at a side face of a fixed end portion thereof constituting aside opposed to the fixation plate 8. Further, a surface of the flexiblecable 9 is mounted with an IC 11 for controlling to drive thepiezoelectric vibrator 10 or the like. Further, the fixation plate 8 forsupporting the respective piezoelectric vibrators 10 is a plate-likemember having a rigidity capable of receiving reaction force from thepiezoelectric vibrators 10, and a metal plate of a stainless steel plateor the like is preferably used therefor.

The casing 2 is a block-like member molded by a thermosetting resin ofan epoxy species resin or the like. Here, the casing 2 is molded by thethermosetting resin because the thermosetting resin is provided with amechanical strength higher than that of a normal resin, a linearexpansion coefficient is smaller than that of a normal resin so thatdeformability depending on the environmental temperature is small.Further, inside of the casing 2 is formed with a container chamber 12capable of containing the vibrator unit 3, and an ink supply path 13constituting a portion of a flow path of ink. Further, the front endface of the casing 2 is formed with a recess 15 for constituting acommon ink reservoir 14.

The container chamber 12 is a hollow portion having a size of capable ofcontaining the vibrator unit 3. At a portion of a front end side of thecontainer chamber 12, a step portion is formed such that a front endface of the fixation plate 8 is brought into contact therewith.

The recess 15 is formed by partially recessing the front end face of thecasing 2 so has to have a substantially trapezoidal shape formed at leftand right outer sides of the container chamber 12.

The ink supply path 13 is formed to penetrate the casing 2 in a heightdirection thereof so that a front end thereof communicates with therecess 15. Further, a rear end portion of the ink supply path 13 isformed at inside of a connecting port 16 projected from the rear endface of the casing 2.

The connection board 5 is a wiring board formed with electric wiringsfor various signals supplied to the recording head 1 and provided with aconnector 17 capable of connecting a signal cable. Further, theconnection board 5 is arranged on the rear end face of the casing 2 andconnected with electric wirings of the flexible cable 9 by soldering orthe like. Further, the connector 17 is inserted with a front end of asignal cable from a control apparatus (not illustrated).

The supply needle unit 6 is a portion connected with an ink cartridge(not illustrated) and is roughly constituted by a needle holder 18, anink supply needle 19 and a filter 20.

The ink supply needle 19 is a portion inserted into the ink cartridgefor introducing ink stored in the ink cartridge. A distal end portion ofthe ink supply needle 19 is sharpened in a conical shape to facilitateto insert into the ink cartridge. Further, the distal end portion isbored with a plurality of ink introducing holes for communicating insideand outside of the ink supply needle 19. Further, since the recordinghead according to the embodiment can eject two kinds of inks, two piecesof the ink supply needles 19 are provided.

The needle holder 18 is a member for attaching the ink supply needle 19,and a surface thereof is formed with base seats 21 for two pieces of theink supply needles 19 for fixedly attaching proximal portions of the inksupply needles 19. The base seat 21 is fabricated in a circular shape incompliance with a shape of a bottom face of the ink supply needle 19.Further, a substantially central portion of the bottom face of the baseseat is formed with an ink discharge port 22 penetrated in a platethickness direction of the needle holder 18. Further, the needle holder18 is extended with a flange portion in a side direction.

The filter 20 is a member for hampering foreign matters at inside of inksuch as dust, burr in dieing and the like from passing therethrough andis constituted by, for example, a metal net having a fine mesh. Thefilter 20 is adhered to a filter holding groove formed at inside of thebase seat 21.

Further, as shown in FIG. 2, the supply needle unit 6 is arranged on therear end face of the casing 2. In the arranging state, the ink dischargeport 22 of the supply needle unit 6 and the connecting port 16 of thecasing 2 are communicated with each other in a liquid tight state via apacking 23.

Next, the above-described flow path unit 4 will be explained. The flowpath unit 4 is constructed by a constitution in which a nozzle plate 31is bonded to one face of a chamber formation plate 30 and an elasticplate 32 is bonded to other face of the chamber formation plate 30.

As shown in FIG. 4, the chamber formation plate 30 is a plate-likemember made of a metal formed with an elongated recess portion 33, acommunicating port 34 and an escaping recess portion 35. According tothe embodiment, the chamber formation plate 30 is fabricated by workinga metal substrate made of nickel having a thickness of 0.35 mm.

An explanation will be given here of reason of selecting nickel of themetal substrate. First reason is that the linear expansion coefficientof nickel is substantially equal to a linear expansion coefficient of ametal (stainless steel in the embodiment as mentioned later)constituting essential portions of the nozzle plate 31 and the elasticplate 32. That is, when the linear expansion coefficients of the chamberformation plate 30, the elastic plate 32 and the nozzle plate 31constituting the flow path unit 4 are substantially equal, in heatingand adhering the respective members, the respective members areuniformly expanded.

Therefore, mechanical stress of warping or the like caused by adifference in the expansion rates is difficult to generate. As a result,even when the adhering temperature is set to high temperature, therespective members can be adhered to each other without trouble.Further, even when the piezoelectric vibrator 10 generates heat inoperating the recording head 1 and the flow path unit 4 is heated by theheat, the respective members 30, 31 and 32 constituting the flow pathunit 4 are uniformly expanded. Therefore, even when heating accompaniedby activating the recording head 1 and cooling accompanied bydeactivating are repeatedly carried out, a drawback of exfoliation orthe like is difficult to be brought about in the respective members 30,31 and 32 constituting the flow path unit 4.

Second reason is that nickel is excellent in corrosion resistance. Thatis, aqueous ink is preferably used in the recording head 1 of this kind,it is important that alteration of rust or the like is not brought abouteven when the recording head 1 is brought into contact with water over along time period. In this respect, nickel is excellent in corrosionresistance similar to stainless steel and alteration of rust or the likeis difficult to be brought about.

Third reason is that nickel is rich in ductility. That is, inmanufacturing the chamber formation plate 30, as mentioned later, thefabrication is carried out by plastic working (for example, forging).Further, the elongated recess portion 33 and the communicating port 34formed in the chamber formation plate 30 are of extremely small shapesand high dimensional accuracy is requested therefor. When nickel is usedfor the metal substrate, since nickel is rich in ductility, theelongated recess portion 33 and the communicating port 34 can be formedwith high dimensional accuracy even by plastic working.

Further, with regard to the chamber formation plate 30, the chamberformation plate 30 may be constituted by a metal other than nickel whenthe condition of the linear expansion coefficient, the condition of thecorrosion resistance and the condition of the ductility are satisfied.

The elongated recess portion 33 is a recess portion in a groove-likeshape constituting a pressure generating chamber 29 and is constitutedby a groove in a linear shape as shown to enlarge in FIG. 5A. Accordingto the embodiment, 180 pieces of grooves each having a width of about0.1 mm, a length of about 1.5 mm and a depth of about 0.1 mm are alignedside by side. A bottom face of the elongated recess portion 33 isrecessed in a V-like shape by reducing a width thereof as progressing ina depth direction (that is, depth side). The bottom face is recessed inthe V-like shape to increase a rigidity of a partition wall 28 forpartitioning the contiguous pressure generating chambers 29. That is, byrecessing the bottom face in the V-like shape, a wall thickness of theproximal portion of the partition wall 28 is thickened to increase therigidity of the partition wall 28. Further, when the rigidity of thepartition wall 28 is increased, influence of pressure variation from thecontiguous pressure generating chamber 29 is difficult to be effected.That is, a variation of ink pressure from the contiguous pressuregenerating chamber 29 is difficult to transmit. Further, by recessingthe bottom face in the V-like shape, the elongated recess portion 33 canbe formed with excellent dimensional accuracy by plastic working (to bementioned later). Further, an angle between the inner faces of therecess portion 33 is, for example, around 90 degrees although prescribedby a working condition.

Further, since a wall thickness of a distal end portion of thepartitioning wall 28 is extremely thin, even when the respectivepressure generating chambers 29 are densely formed, a necessary volumecan be ensured.

Both longitudinal end portions of the elongated recess portion 33 aresloped downwardly to inner sides as progressing to the depth side. Theboth end portions are constituted in this way to form the elongatedrecess portion 33 with excellent dimensional accuracy by plasticworking.

Further, contiguous to the elongated recess portion 33 at the both endsof the row, there are formed single ones of dummy recesses 36 having awidth wider than that of the elongated recess portion 33. The dummyrecess portion 36 is a recess portion in a groove-like shapeconstituting a dummy pressure generating chamber which is not related toejection of ink drops. The dummy recess portion 36 according to theembodiment is constituted by a groove having a width of about 0.2 mm, alength of about 1.5 mm and a depth of about 0.1 mm. Further, a bottomface of the dummy recess portion 36 is recessed in a W-like shape. Thisis also for increasing the rigidity of the partition wall 28 and formingthe dummy recess portion 36 with excellent dimensional accuracy byplastic working.

Further, a row of recesses is constituted by the respective elongatedrecess portions 33 and the pair of dummy recess portions 36. Accordingto the embodiment, two rows of the recesses are formed as shown in FIG.4.

The communicating port 34 is formed as a small through hole penetratingfrom one end of the elongated recess portion 33 in a plate thicknessdirection. The communicating ports 34 are formed for respective ones ofthe elongated recess portions 33 and are formed by 180 pieces in asingle recess portion row. The communicating port 34 of the embodimentis in a rectangular shape in an opening shape thereof and is constitutedby a first communicating port 37 formed from a side of the elongatedrecess portion 33 to a middle in the plate thickness direction in thechamber formation plate 30 and a second communicating port 38 formedfrom a surface thereof on a side opposed to the elongated recess portion33 up to a middle in the plate thickness direction.

Further, sectional areas of the first communicating port 37 and thesecond communicating port 38 differ from each other and an innerdimension of the second communicating port 38 is set to be slightlysmaller than an inner dimension of the first communicating port 37. Thisis caused by manufacturing the communicating port 34 by pressing. Thechamber formation plate 30 is fabricated by working a nickel platehaving a thickness of 0.35 mm, a length of the communicating port 34becomes equal to or larger than 0.25 mm even when the depth of therecess portion 33 is subtracted. Further, the width of the communicatingport 34 needs to be narrower than the groove width of the elongatedrecess portion 33, set to be less than 0.1 mm. Therefore, when thecommunicating port 34 is going to be punched through by a single time ofworking, a male die (punch) is buckled due to an aspect ratio thereof.

Therefore, in the embodiment, the working is divided into two steps. Inthe first step, the first communicating port 37 is formed halfway in theplate thickness direction, and in the second step, the secondcommunicating port 38 is formed. The working process of thiscommunicating port 34 will be described later.

Further, the dummy recess portion 36 is formed with a dummycommunicating port 39. Similar to the above-described communicating port34, the dummy communicating port 39 is constituted by a first dummycommunicating port 40 and a second dummy communicating port 41 and aninner dimension of the second dummy communicating port 41 is set to besmaller than an inner dimension of the first dummy communicating port40.

Further, although according to the embodiment, the communicating port 34and the dummy communicating port 39 opening shapes of which areconstituted by small through holes in a rectangular shape areexemplified, the invention is not limited to the shape. For example, theshape may be constituted by a through hole opened in a circular shape ora through hole opened in a polygonal shape.

The escaping recess portion 35 forms an operating space of a complianceportion 46 (described later) in the common ink reservoir 14. Accordingto the embodiment, the escaping recess portion 35 is constituted by arecess portion in a trapezoidal shape having a shape substantially thesame as that of the recess 15 of the casing 2 and a depth equal to thatof the elongated recess portion 33.

Next, the above-described elastic plate 32 will be explained. Theelastic plate 32 is a kind of a sealing plate of the invention and isfabricated by, for example, a composite material having a two-layerstructure laminating an elastic film 43 on a support plate 42. Accordingto the embodiment, a stainless steel plate is used as the support plate42 and PPS (polyphenylene sulphide) is used as the elastic film 43.

As shown in FIG. 6, the elastic plate 32 is formed with a diaphragmportion 44, an ink supply port 45 and the compliance portion 46.

The diaphragm portion 44 is a portion for partitioning a portion of thepressure generating chamber 29. That is, the diaphragm portion 44 sealsan opening face of the elongated recess portion 33 and forms topartition the pressure generating chamber 29 along with the elongatedrecess portion 33. As shown in FIG. 7A, the diaphragm portion 44 is of aslender shape in correspondence with the elongated recess portion 33 andis formed for each of the elongated recess portions 33 with respect to asealing region for sealing the elongated recess portion 33.Specifically, a width of the diaphragm portion 44 is set to besubstantially equal to the groove width of the elongated recess portion33 and a length of the diaphragm portion 44 is set to be a slightshorter than the length of the elongated recess portion 33. With regardto the length, the length is set to be about two thirds of the length ofthe elongated recess portion 33. Further, with regard to a position offorming the diaphragm portion 44, as shown in FIG. 2, one end of thediaphragm portion 44 is aligned to one end of the elongated recessportion 33 (end portion on a side of the communicating port 34).

As shown in FIG. 7B, the diaphragm portion 44 is fabricated by removingthe support plate 42 at a portion thereof in correspondence with theelongated recess portion 33 by etching or the like to constitute onlythe elastic film 43 and an island portion 47 is formed at inside of thering. The island portion 47 is a portion bonded with a distal end faceof the piezoelectric vibrator 10.

The ink supply port 45 is a hole for communicating the pressuregenerating chamber 29 and the common ink reservoir 14 and is penetratedin a plate thickness direction of the elastic plate 32. Similar to thediaphragm portion 44, also the ink supply port 45 is formed to each ofthe elongated recess portions 33 at a position in correspondence withthe elongated recess portion 33. As shown in FIG. 2, the ink supply port45 is bored at a position in correspondence with other end of theelongated recess portion 33 on a side opposed to the communicating port34. Further, a diameter of the ink supply port 45 is set to besufficiently smaller than the groove width of the elongated recessportion 33. According to the embodiment, the ink supply port 45 isconstituted by a small through hole of 23 μm.

Reason of constituting the ink supply port 45 by the small through holein this way is that flow path resistance is provided between thepressure generating chamber 29 and the common ink reservoir 14. That is,according to the recording head 1, an ink drop is ejected by utilizing apressure variation applied to ink at inside of the pressure generatingchamber 29. Therefore, in order to efficiently eject an ink drop, it isimportant that ink pressure at inside of the pressure generating chamber29 is prevented from being escaped to a side of the common ink reservoir14 as less as possible. From the view point, the ink supply port 45 isconstituted by the small through hole.

Further, when the ink supply port 45 is constituted by the through holeas in the embodiment, there is an advantage that the working isfacilitated and high dimensional accuracy is achieved. That is, the inksupply port 45 is the through hole, can be fabricated by lasermachining. Therefore, even a small diameter can be fabricated with highdimensional accuracy and also the operation is facilitated.

The compliance portion 46 is a portion for partitioning a portion of thecommon ink reservoir 14. That is, the common ink reservoir 14 is formedto partition by the compliance portion 46 and the recess 15. Thecompliance portion 46 is of a trapezoidal shape substantially the sameas an opening shape of the recess 15 and is fabricated by removing aportion of the support plate 42 by etching or the like to constituteonly the elastic film 43.

Further, the support plate 42 and the elastic film 43 constituting theelastic plate 32 are not limited to the example. Further, polyimide maybe used as the elastic film 43. Further, the elastic plate 32 may beconstituted by a metal plate provided with a thick wall and a thin wallat a surrounding of the thick wall for constituting the diaphragmportion 44 and a thin wall for constituting the compliance portion 46.

Next, the above-described nozzle plate 31 will be explained. The nozzleplate 31 is a plate-like member made of a metal aligned with a pluralityof nozzle orifices 48 at a pitch in correspondence with a dot formingdensity. According to the embodiment, a nozzle row is constituted byaligning a total of 180 pieces of the nozzle orifices 48 and two rows ofthe nozzles are formed as shown in FIG. 2.

Further, when the nozzle plate 31 is bonded to other face of the chamberformation plate 30, that is, to a surface thereof on a side opposed tothe elastic plate 32, the respective nozzle orifices 48 face thecorresponding communicating ports 34.

Further, when the above-described elastic plate 32 is bonded to onesurface of the chamber formation plate 30, that is, a face thereof forforming the elongated recess portion 33, the diaphragm portion 44 sealsthe opening face of the elongated recess portion 33 to form to partitionthe pressure generating chamber 29. Similarly, also the opening face ofthe dummy recess portion 36 is sealed to form to partition the dummypressure generating chamber. Further, when the above-described nozzleplate 31 is bonded to other surface of the chamber formation plate 30,the nozzle orifice 48 faces the corresponding communicating port 34.When the piezoelectric vibrator 10 bonded to the island portion 47 isextended or contracted under the state, the elastic film 43 at asurrounding of the island portion is deformed and the island portion 47is pushed to the side of the elongated recess portion 33 or pulled in adirection of separating from the side of the elongated recess portion33. By deforming the elastic film 43, the pressure generating chamber 29is expanded or contracted to provide a pressure variation to ink atinside of the pressure generating chamber 29.

When the elastic plate 32 (that is, the flow path unit 4) is bonded tothe casing 2, the compliance portion 46 seals the recess 15. Thecompliance portion 46 absorbs the pressure variation of ink stored inthe common ink reservoir 14. That is, the elastic film 43 is deformed inaccordance with pressure of stored ink. Further, the above-describedescaping recess portion 35 forms a space for allowing the elastic film43 to be expanded.

In a case where the compliance portion 46 is omitted while reducing thevolume of the common ink reservoir 14, the escaping recess portion 35may serve as a part of the common ink reservoir. Further, the escapingrecess portion 35 may be formed as a through hole so that the obtainedspace is used as a part of the common ink reservoir.

The recording head 1 having the above-described constitution includes acommon ink flow path from the ink supply needle 19 to the common inkreservoir 14, and an individual ink flow path reaching each of thenozzle orifices 48 by passing the pressure generating chamber 29 fromthe common ink reservoir 14. Further, ink stored in the ink cartridge isintroduced from the ink supply needle 19 and stored in the common inkreservoir 14 by passing the common ink flow path. Ink stored in thecommon ink reservoir 14 is ejected from the nozzle orifice 48 by passingthe individual ink flow path.

For example, when the piezoelectric vibrator 10 is contracted, thediaphragm portion 44 is pulled to the side of the vibrator unit 3 toexpand the pressure generating chamber 29. By the expansion, inside ofthe pressure generating chamber 29 is brought under negative pressure,ink at inside of the common ink reservoir 14 flows into each pressuregenerating chamber 29 by passing the ink supply port 45. Thereafter,when the piezoelectric vibrator 10 is extended, the diaphragm portion 44is pushed to the side of the chamber formation plate 30 to contract thepressure generating chamber 29. By the contraction, ink pressure atinside of the pressure generating chamber 29 rises and an ink drop isejected from the corresponding nozzle orifice 48.

According to the recording head 1, the bottom face of the pressuregenerating chamber 29 (elongated recess portion 33) is recessed in theV-like shape. Therefore, the wall thickness of the proximal portion ofthe partition wall 28 for partitioning the contiguous pressuregenerating chambers 29 is formed to be thicker than the wall thicknessof the distal end portion. Thereby, the rigidity of the thick wall 28can be increased. Therefore, in ejecting an ink drop, even when avariation of ink pressure is produced at inside of the pressuregenerating chamber 29, the pressure variation can be made to bedifficult to transmit to the contiguous pressure generating chamber 29.As a result, the so-called contiguous cross talk can be prevented andejection of ink drop can be stabilized.

According to the embodiment, the ink supply port 45 for communicatingthe common ink reservoir 14 and the pressure generating chamber 29 isconstituted by the small hole penetrating the elastic plate 32 in theplate thickness direction, high dimensional accuracy thereof is easilyachieved by laser machining or the like. Thereby, an ink flowingcharacteristic into the respective pressure generating chambers 29(flowing velocity, flowing amount or the like) can be highly equalized.Further, when the fabrication is carried out by the laser beam, thefabrication is also facilitated.

According to the embodiment, there are provided the dummy pressuregenerating chambers which are not related to ejection of ink dropcontiguously to the pressure generating chambers 29 at end portions ofthe row (that is, a hollow portion partitioned by the dummy recessportion 36 and the elastic plate 32), with regard to the pressuregenerating chambers 29 at both ends, one side thereof is formed with thecontiguous pressure generating chamber 29 and an opposed thereof isformed with the dummy pressure generating chamber. Thereby, with regardto the pressure generating chambers 29 at end portions of the row, therigidity of the partition wall partitioning the pressure generatingchamber 29 can be made to be equal to the rigidity of the partition wallat the other pressure generating chambers 29 at a middle of the row. Asa result, ink drop ejection characteristics of all the pressuregenerating chambers 29 of the one row can be made to be equal to eachother.

With regard to the dummy pressure generating chamber, the width on theside of the aligning direction is made to be wider than the width of therespective pressure generating chambers 29. In other words, the width ofthe dummy recess portion 36 is made to be wider than the width of theelongated recess portion 33. Thereby, ejection characteristics of thepressure generating chamber 29 at the end portion of the row and thepressure generating chamber 29 at the middle of the row can be made tobe equal to each other with high accuracy.

According to the embodiment, the recess 15 is formed by partiallyrecessing the front end face of the casing 2, the common ink reservoir14 is formed to partition by the recess 15 and the elastic plate 32, anexclusive member for forming the common ink reservoir 14 is dispensedwith and simplification of the constitution is achieved. Further, thecasing 2 is fabricated by resin dieing, fabrication of the recess 15 isalso relatively facilitated.

Next, a method of manufacturing the recording head 1 will be explained.Since the manufacturing method is characterized in steps ofmanufacturing the chamber formation plate 30, an explanation will bemainly given for the steps of manufacturing the chamber formation plate30.

The chamber formation plate 30 is fabricated by forging by a progressivedie. Further, a metal strip 55 (referred to as “strip 55” in thefollowing explanation) used as a material of the chamber formation plate30 is made of nickel as described above.

The steps of manufacturing the chamber formation plate 30 comprisessteps of forming the elongated recess portion 33 and steps of formingthe communicating port 34 which are carried out by a progressive die.

In the elongated recess portion forming steps, a male die 51 shown inFIGS. 8A and 8B and a female die shown in FIGS. 9A and 9B are used. Themale die 51 is a die for forming the elongated recess portion 33. Themale die is aligned with projections 53 for forming the elongated recessportions 33 by a number the same as that of the elongated recessportions 33. Further, the projections 53 at both ends in an aligneddirection are also provided with dummy projections (not illustrated) forforming the dummy recess portions 36. A distal end portion 53 a of theprojection 53 is tapered from a center thereof in a width direction byan angle of about 45 degrees as shown in FIG. 8B. Thereby, the distalend portion 53 a is sharpened in the V-like shape in view from alongitudinal direction thereof. Further, both longitudinal ends of thedistal end portions 53A are tapered by an angle of about 45 degrees asshown in FIG. 8A. Therefore, the distal end portion 53 a of theprojection 53 is formed in a shape of tapering both ends of a triangularprism.

Further, the female die 52 is formed with a plurality of projections 54at an upper face thereof. The projection 54 is for assisting to form thepartition wall partitioning the contiguous pressure generating chambers29 and is disposed between the elongated recess portions 33. Theprojection 54 is of a quadrangular prism, a width thereof is set to be aslight narrower than an interval between the contiguous pressuregenerating chambers 29 (thickness of partition wall) and a heightthereof is set to a degree the same as that of the width. A length ofthe projection 54 is set to a degree the same as that of a length of theelongated recess portion 33 (projection 53).

In the elongated recess portion forming steps, first, as shown in FIG.10A, the strip 55 is mounted at an upper face of the female die 52 andthe male die 51 is arranged on an upper side of the strip 55. Next, asshown in FIG. 10B, the male die 51 is moved down to push the distal endportion of the projection 53 into the strip 55. At this occasion, sincethe distal end portion 53 a of the projection 53 is sharpened in theV-like shape, the distal end portion 53 a can firmly be pushed into thestrip 55 without buckling. Pushing of the projection 53 is carried outup to a middle in a plate thickness direction of the strip 55 as shownin FIG. 10C.

By pushing the projection 53, a portion of the strip 55 flows to formthe elongated recess portion 33. In this case, since the distal endportion 53 a of the projection 53 is sharpened in the V-like shape, eventhe elongated recess portion 33 having a small shape can be formed withhigh dimensional accuracy. That is, the portion of the strip 55 pushedby the distal end portion 53 a flows smoothly, the elongated recessportion 33 to be formed is formed in a shape following the shape of theprojection 53. Further, since the both longitudinal ends of the distalend portion 53 a are tapered, the strip 55 pushed by the portions alsoflows smoothly. Therefore, also the both end portions in thelongitudinal direction of the elongated recess portion 33 are formedwith high dimensional accuracy.

Since pushing of the projection 53 is stopped at the middle of the platethickness direction, the strip 55 thicker than in the case of forming athrough hole can be used. Thereby, the rigidity of the chamber formationplate 30 can be increased and improvement of an ink ejectioncharacteristic is achieved. Further, the chamber formation plate 30 iseasily dealt with and the operation is advantageous also in enhancingplane accuracy.

A portion of the strip 55 is raised into a space between the contiguousprojections 53 by being pressed by the projections 53. In this case, theprojection 54 provided at the female die 52 is arranged at a position incorrespondence with an interval between the projections 53, flow of thestrip 55 into the space is assisted. Thereby, the strip 55 canefficiently be introduced into the space between the projections 53 andthe protrusion (i.e., the partition wall 28) can be formed highly.

Plastic working is performed on the strip (material) 55 by the male die51 and the female die 52 under condition of room temperature, andplastic working described below is performed similarly under conditionof room temperature.

The elongated recess portion 33 is formed basically as described above.Precision in the formation of the elongated recess portion 33,particularly, how to mold the partition wall 28 is important. In orderto meet such needs, in the invention, a forging punch is caused tocomprise a first die and a second die including a preforming die and afinishing die, and a special shape is given to the second die to formthe proper partition wall 28.

As shown in FIG. 11, large number of molding punches 51 b are arrangedin the male die 51 a, that is, the first die. In order to form theelongated recess portions 33, the molding punches 51 b are elongated toform projections 53 c. The projections 53 c are arranged in parallel ata predetermined pitch. In order to form the partition walls 28, gaps 53b (see FIG. 12B) are provided between the molding punches 51 b. A statein which the first die 51 a is pushed into the chamber formation plate30 (strip 55) to be a worked object is shown in FIG. 12C.

In this embodiment, the material (strip) 55 is caused to flow into thegaps 53 b by the preforming die 56 and the distribution of the material55 in the gaps 53 b is caused to approach a normal state as much aspossible by the finishing die 57. Consequently, the amount of the flowof the material into the gaps 53 b is brought into an almost straightstate in the longitudinal direction of the gaps 53 b, which isconvenient for the case in which that portions are caused to serve as amember such as the partition wall 28 of the pressure generating chambers29 of the liquid ejection head 1.

The structure and operation of the second die 52 a will be described indetail as follows.

As shown in FIG. 12A, in a female die 52 a, that is, the second die,each of projections 54 is formed with a concave portion 54 a at aportion corresponding to the longitudinal middle part of the projection53 c. The preforming die 56 is provided with the projections 54 opposedto the gaps 53 b and having almost the same length as the length of thegaps 53 b.

FIG. 14A enlargedly shows the concave portion 54 a. FIG. 14B shows across section of a part of the projection 54 other than the concaveportion 54 a. FIG. 14C shows a cross section of a part of the projection54 where the concave portion 54 a is formed.

The projection 54 conceptually shown in FIGS. 9A through 10C is a convexmember having a small height. In order to form the concave portion 54 a,a certain height is actually required for the projection 54. In order toobtain such a certain height, each of the projections 54 has awedge-shaped cross section as shown in FIG. 12B. The angle of thewedge-shaped portion is set to be an angle of 90 degrees or less. Valleyportions 56 a are defined between the adjacent projections 54.

As shown in FIGS. 12B and 12C, the material 55 opposed to the gaps 53 bis pressed by the projections 54 plastically flows toward the gaps 53 bdirectly. Incidentally, the projections 54 may be laterally shifted by ahalf-pitch so that the projections 54 are disposed in opposition to theprojections 53 c, respectively, as shown in FIG. 12E. In this case, anamount of material deformation to be compressed between the projections54 and the projections 53 c becomes largest. Accordingly, the parts ofthe material 55 respectively located between the opposed tip edges ofthe projections 53 c and 54 flow obliquely upward of the projections 54shown in FIG. 12E, and is pressed into the gaps 53 b. Thus, the materialflows into each gap 53 b from both sides thereof so that sufficientmolding accuracy can be attained.

The length of the concave portion 54 a of the projection 54 in thelongitudinal direction is set to be approximately ⅔ of the length of theprojection 54 or less. Preferably, it is ½ of the length of theprojection 54 or less. The pitch of the projection 54 is set to be 0.14mm. The pitch of the projection 54 is set to be 0.3 mm or less so thatmore suitable preforming is carried out in a forging work of a componentsuch as the liquid ejection head. The pitch is preferably 0.2 mm or lessand more preferably 0.15 mm or less. Furthermore, at least the concaveportion 54 a of the projection 54 has a surface thereof finishedsmoothly. For the finishing, mirror finishing is suitable, andfurthermore, chromium plating may be carried out.

As shown in FIG. 15, a ratio of a length L2 of the concave portion 54 ato a length L1 of the projections 54, i.e., L2/L1, is selected to be ⅔or less, preferably ½ or less. H denotes a length from the bottom part56 a to the tip of the projections 54, viz., a height of the projection54. D denotes a depth of the concave portion 54 a. To secure goodplastic flow of the material at the gaps 53 b, predetermined dimensionalratios are set up among those parts.

Specifically, a ratio of the depth D of the concave portion 54 a to thelength L2 of the concave portion 54 a is about 0.05 to 0.3. In thisinstance, an actual length L2 is within 0.5 mm to 1 mm, and the depth Dis within 0.05 mm to 0.15 mm. A ratio of the depth D of the concaveportion 54 a to the height H of the projections 54 is within about 0.5to 1. In this instance, an actual height H is within 0.5 mm to 1.5 mm.The length L1 of the projections 54 is 1.6 mm in this instance, andaccordingly, L2/L1 is within 0.31 to 0.62.

FIG. 16A is a first modified example of the preforming die 56. In thiscase, a reinforcing convex portion 54 d is provided at a mid part of theconcave portion 54 a. At the time of pressure forming operation, a forceto expand the concave portion 54 a acts on the preforming die 56. Astress concentrates on the deepest part of the concave portion 54 a sothat the deepest part is likely to crack. With provision of thereinforcing convex portion 54 d, however, no stress concentrates on thedeepest part of the concave portion, and hence, there is no chance thatthe deepest part cracks.

FIG. 16B shows a second modified example of the preforming die 56. Inthis case, a relief recess 54 e is provided at a mid part of the concaveportion 54 a. The material 55 flowing into the concave portion 54 apresses the deepest part of the concave portion 54 a so that the deepestpart is likely to crack. With provision of the relief recess 54 e,however, no pressure application to the deepest part of the concaveportion occurs. There is no anxiety that the deepest part cracks.

FIG. 17A shows a third modified example of the preforming die 56 inwhich the convex portion 54 a is formed with flat faces. FIG. 17B showsa fourth modified example of the preforming die 56 in which only bottomcorners of the convex portion 54 a are curved. FIG. 17C shows a fifthmodified example of the preforming die 56 in which the convex portion 54a is formed with sloped flat side faces and a flat bottom face. FIG. 17Dshows a sixth modified example of the preforming die 56 in which theconvex portion 54 b substantially defines two concave portions 54 b atboth sides thereof. FIG. 17E shows a seventh example of the preformingdie 56 in which a top of the convex portion 54 b shown in FIG. 17D ismade flat.

While the projection 54 is wedge-shaped and has a sharp tip portion, aflat top surface 54 c or a rounded tip portion may be formed as shown inFIG. 17F depending on the moving condition of the material 55.

The finishing die 57 is used after the primary molding using thepreforming die 56. As shown in FIG. 13A, the finishing die 57 is formedwith flat surfaces 57 a located both sides of a concave portion 57 b.The flat surfaces 57 a and the concave portion 57 b are extendedentirely in the longitudinal direction of the finishing die 57. Theconcave portion 57 b is located at a part corresponding to the concaveportions 54 a of the projections 54 in the preforming die 56.

Slope faces 57 c are provided both longitudinal ends of each flatsurface 57 a such that portions closer to the ends are lowered.

FIG. 18A is a first modified example of the finishing die 57. In thiscase, a reinforcing convex portion 57 d is provided at a mid part of theconcave portion 57 b. At the time of pressure forming operation, a forceto expand the concave portion 57 b acts on the finishing die 57. Astress concentrates on the deepest part of the concave portion 57 b sothat the deepest part is likely to crack. With provision of thereinforcing convex portion 57 d, however, no stress concentrates on thedeepest part of the concave portion, and hence, there is no chance thatthe deepest part cracks.

FIG. 18B shows a second modified example of the finishing die 57. Inthis case, a relief recess 57 e is provided at a mid part of the concaveportion 57 b. The material 55 flowing into the concave portion 57 bpresses the deepest part of the concave portion 57 b so that the deepestpart is likely to crack. With provision of the relief recess 57 e,however, no pressure application to the deepest part of the concaveportion occurs. There is no anxiety that the deepest part cracks.

A depth and a length of the concave portion 57 b of the finishing die 57are 0.05 to 0.15 mm and 0.5 to 1 mm, respectively. In this case, in afinishing work, an amount of material flowing in a directionsubstantially orthogonal to the pressing direction is satisfactorilybalanced with the concave portion 57 b for receiving the material inview of a magnitude of a pressing stroke. Accordingly, the material flowinto the gaps 53 b is optimized.

FIG. 19 shows a third modified example of the finishing die 57 in whicha height difference T is provided between the flat surfaces 57 a. Morespecifically, one flat surface 57 a which is placed at a portion to becloser to the communicating port 34 of the pressure generating chamber29 is lower than the other flat surface 57 a. Therefore, an amount ofthe material 55 pressed by the flat surface 57 a closer to thecommunication port 34 is smaller than that of the material 55 pressed bythe other flat surface 57 a, so that a density or hardness of thematerial closer to the communication port 34 are lower than those of theother side. Accordingly, the work resistance acting on a punch used forforming of the communication port 34 is reduced, so that durability ofthe punch is improved, and this feature is advantageous in improving theworking accuracy of the communication port 34.

A longitudinal width dimension of each projection 54 in the preformingdie 56 and a width dimension of the finishing die 57 in a directionorthogonal to the elongated concave portion 57 b are each equal to alongitudinal size of the pressure generating chamber 29.

As shown in FIG. 20A, the chamber formation plate 30 and the nozzleplate 31 are joined together in a state that dents 63 are formed in thesurface of the chamber formation plate 30, which is closer to the nozzleplate 31. There are many ways to arrange the dents 63. In thisembodiment, as shown in FIG. 12B, when the elongated recess portions 33are temporarily formed, indentations to be the dents 63 are formed asthe result of press-fitting of the projections 54. Actually, althoughthose indentations by the projections 54 are groove-shaped, the showndents are left at a location near the communication port 34 after thepolish finishing step.

When the chamber formation plate 30 and the nozzle plate 31 are joinedtogether by the adhesive 64, excessive adhesive 64 is received in thedents 63. Accordingly, a thickness of the adhesive layer 64 isoptimized, so that the bonding strength between the chamber formationplate 30 and the nozzle plate 31 is increased.

FIG. 20B shows an arrangement of the dents 63 in a case where theprojections 54 are arranged as shown in FIG. 12C. FIG. 20C shows anarrangement of the dents 63 in a case where the projections 54 arearranged as shown in FIG. 12E. In either case, a pitch of the dents 63is substantially equal to that of the pressure generating chamber 29(the elongated recess portions 33).

If the dents 63 are so arranged, the dents 63 are distributed at regularspatial intervals on the joining surface of the chamber formation plate30, which is closer to the nozzle plate 31. As a result, the dents 63uniformly receives the excessive adhesive 64, so that the thickness ofthe adhesive layer 64 is optimized over a broad area, and the bondingstrength is increased. Further, since the dents 63 are each located nearthe opening of the communication port 34, no excessive adhesive 64overflows into a passage space of the communication port 34.Accordingly, there is no chance that air bubbles stay at the locationswhere the adhesive overflows, and a good ink flow is secured.

Next, description will be given to the operation of the forging punchconstituted by the first die 51 a and the second die 52 a.

FIG. 12B shows a state obtained immediately before the material (strip)55 is pressurized between the first die 51 a and the second die 52 a.When the projections 54 are pressed into the material 55 as shown inFIGS. 12C and 12D, the material is caused to flow into the gaps 53 b sothat the partition wall 28 is preformed.

Incidentally, the second die 52 a is provided with the concave portion54 a having a small height in a middle part. In portions 56 b close tothe ends of the second die 52 a on both sides of the concave portion 54a (see FIG. 12D), an interval D1 between both of the dies 51 a and 52 ais smaller than an interval D2 between the middle parts thereof wherethe concave portion 54 a is formed. In this narrow portion, the amountof the pressurization of the material is increased so that the materialthus pressurized is caused to flow to be pushed out in a direction whichis almost orthogonal to the direction of the pressurization. That is,the material is moved toward the concave portion 54 a in which theamount of the pressurization is smaller. In other words, the concaveportion 54 a serves to provide a place into which the material 55escapes. Such a material movement is mainly carried out in thelongitudinal direction of the projections 53 c or the gaps 53 b, so thata part of the material 55 becomes a bulged portion 55 a which isprotruded into the concave portion 54 a.

Furthermore, a much larger amount of the material 55 is positivelypushed into the gaps 53 b by the contribution of the sufficient heightof the projections 54. In the partition wall 28 set in such a preformingstate, lower portions 28 a and a higher portion 28 b are formed as shownin FIG. 12D. Such a difference in the height is made because a largeramount of the material 55 pressurized in the end portions 56 b flows tothe concave portion 54 a while a large amount of the material 55 flowsinto the gaps 53 b simultaneously.

Moreover, since the projections 53 c are arranged at a predeterminedpitch, the plastic flow of the material in the transverse direction ofthe projections 53 c caused by the press-fitting operation is smoothlymade uniform for both the direction of the flow and the amount of theflow.

Since the material 55 flowing into the gaps 53 b as configured the aboveconstitutes the partition wall 28 of the elongated recess portions 33,the shape of the elongated recess portion 33 can be formed accurately.For forming such a minute structure, an anisotropic etching method isgenerally employed. Since such a method requires a large processingman-hour, it is disadvantageous in respect of the manufacturing cost. Onthe other hand, if the forging punch is used for a metallic materialsuch as nickel, the processing man-hour is considerably reduced.Furthermore, since the processing can be carried out with a uniformvolume of each elongated recess portion 33, in a case where the pressuregenerating chamber of the liquid ejection head is to be formed, theejection performance of the liquid ejection head is stabilized.

Since the concave portion 54 a takes the shape of an arcuate concaveportion, the height of the middle part of the second die is graduallychanged. Consequently, the amount of the material 55 flowing into thegaps 53 b becomes as uniform as possible in the longitudinal directionof the gaps 53 b. In a case where the concave portion 54 a is formedwith a plurality of flat faces, it is possible to obtain the same effectby selecting the inclination angle of the sloped flat faces.

In a case where the convex portion 54 b is provided in the middle partof the concave portion 54 b, a plurality of concave portions 54 a aredefined so that portions in which the amount of the pressurization islarge and portions in which the amount of the pressurization is smallare alternately provided. Accordingly, the portions (corresponding to 56b) in which the amount of the pressurization is large and the concaveportion 54 a to which the material 55 is flown are alternately providedwith small pitches. Consequently, the amount of the material 55 flowingto the gaps 53 b is almost uniform in the longitudinal direction of thegaps 53 b.

Since the concave portion. 54 a is formed in the mid part of theprojection 54 in the longitudinal direction thereof, the materialequally flows from both sides of the concave portion 54 a. As a result,the flow amount of the material is made uniform over the entire lengthof the concave portion 54 a. For example, in a case of forming thepartitioning walls 28 of the pressure generating chambers 29, thepartitioning walls 28 can be obtained with high accuracy.

By selecting a length of the concave portion 54 a in the longitudinaldirection of the projections 54 to be about ⅔ as large as a length ofthe projection 54, an amount of material flowing in a directionsubstantially orthogonal to the pressing direction is satisfactorilybalanced with the size of the concave portion 54 a for receiving thematerial in view of a magnitude of a pressing stroke. Accordingly, thematerial flow into the gaps 53 b is optimized.

In a case where a ratio of the depth D of the concave portion 54 a tothe length L2 of the concave portion 54 a is about 0.05 to 0.3 or a casewhere a ratio of the depth D of the concave portion 54 a to the height Hof the projections 54 is about 0.5 to 1, the above advantages can beobtained more surely.

Since at least the concave portion 54 a of the projection 54 has asurface thereof finished smoothly by mirror finishing or chromiumplating, the flow direction of the material 55 is positively changedtoward the gaps 53 b so that the flow of the material into the gaps 53 bcan be carried out more positively.

When the primary molding shown in FIGS. 12C and 12D is completed, thematerial 55 is moved between the first die 51 a and the finishing die 57as shown in FIG. 13B, and is pressurized therein by both of the dies 51a and 52 a as shown in FIG. 13C. The flat surfaces 57 a increases theamount of the material 55 flowing into the gaps 53 b so that the heightsof the lower portions 28 a are increased. Incidentally, since the bulgedportion 55 a is accommodated in the concave portion 57 b and does notreceive pressurizing force from the finishing die 57, the height of thehigher portion 28 b is rarely changed. Accordingly, the height of thepartition wall 28 finally becomes almost uniform as shown in FIG. 13D.

In the finishing forming stage, since the slope faces 57 c are formed,the amount of the material 55 flowing into each gaps 53 b is caused tobe as uniform as possible in all the gaps 53 b. Namely, the material 55flows in the arrangement direction of the projections 53 little bylittle from the central part of the array of the projections 53 towardthe both ends thereof so that the vicinity of the ends of the materialare made thick due to the accumulation of the plastic flow. Since thethick portions are pressurized by the slope faces 57 c which arelowered, the material in the thick portions can be prevented fromexcessively flowing into the gaps 53 b. Accordingly, the amount of theflow of the material 55 can be as uniform as possible in all the gaps 53b.

Since the projection 54 takes the shape of a wedge having a sharp tip(the wedge angle is 90 degrees or less), the wedge-shaped portionreliably cuts into the material 55 so that the material 55 in theportions opposed to the gaps 53 b can be accurately pressurized and theflow of the material into the gaps 53 b can be carried out reliably.Further, since the pitch of the projections 54 is set to be 0.3 mm orless, the pressure generating chamber of the liquid ejection head can beprecisely fabricated by the forging punch.

The first die 51 a and, the second die 52 a are fixed to an ordinaryforging device (not shown), and the chamber formation plate 30 (thestrip 55) is provided between both of the dies 51 a and 52 a so that theforging work is progressively carried out. Moreover, the second die 52 ais constituted by the preforming die 56 and the finishing die 57 inpairs. Therefore, it is preferable that the preforming die 56 and thefinishing die 57 are arranged adjacently to each other so that thechamber formation plate 30 (the strip 55) is sequentially moved.

Further, since the second die 52 a includes the preforming die 56 whichfirst operates to perform the primary molding, and the finishing die 57which subsequently operates to perform the secondary molding, theforging work is efficiently performed in a progressive manner.Therefore, the positioning operation of the worked object in each stagecan be precisely performed so that the molding accuracy is enhanced.

As a second example, a recording head 1′ shown in FIG. 21 adopts a heatgenerating element 61 as the pressure generating element. According tothe embodiment, in place of the elastic plate 32, a sealing board 62provided with the compliance portion 46 and the ink supply port 45 isused and the side of the elongated recess portion 33 of the chamberformation plate 30 is sealed by the sealing board 62. Further, the heatgenerating element 61 is attached to a surface of the sealing board 62at inside of the pressure generating chamber 29. The heat generatingelement 61 generates heat by feeding electricity thereto via an electricwiring.

Since other constitutions of the chamber formation plate 30, the nozzleplate 31 and the like are similar to those of the above-describedembodiments, explanations thereof will be omitted.

In the recording head 1′, by feeding electricity to the heat generatingelement 61, ink at inside of the pressure generating chamber 29 isbumped and bubbles produced by the bumping presses ink at inside of thepressure generating chamber 29, so that ink drops are ejected from thenozzle orifice 48.

Even in the case of the recording head 1′, since the chamber formationplate 30 is fabricated by plastic working of metal, advantages similarto those of the above-described embodiments are achieved.

With regard to the communicating port 34, although according to theabove-described embodiments, an example of providing the communicatingport 34 at one end portion of the elongated recess portion 33 has beenexplained, the invention is not limited thereto. For example, thecommunicating port 34 may be formed substantially at center of theelongated recess portion 33 in the longitudinal direction and the inksupply ports 45 and the common ink reservoirs 14 communicated therewithmay be arranged at both longitudinal ends of the elongated recessportion 33. Thereby, stagnation of ink at inside of the pressuregenerating chamber 29 reaching the communicating port 34 from the inksupply ports 45 can be prevented.

Further, although according to the above-described embodiments, anexample of applying the invention to the recording head used in the inkjet recording apparatus has been shown, an object of the liquid ejectionhead to which the invention is applied is not constituted only by ink ofthe ink jet recording apparatus but glue, manicure, conductive liquid(liquid metal) or the like can be ejected.

For example, the invention is applicable to a color filter manufacturingapparatus to be used for manufacturing a color filter of aliquid-crystal display. In this case, a coloring material ejection headof the apparatus is an example of the liquid ejection head. Anotherexample of the liquid ejection apparatus is an electrode formationapparatus for forming electrodes, such as those of an organic EL displayor those of a FED (Field Emission Display). In this case, an electrodematerial (a conductive paste) ejection head of the apparatus is anexample of the liquid ejection head. Still another example of the liquidejection apparatus is a biochip manufacturing apparatus formanufacturing a biochip. In this case, a bio-organic substance ejectionhead of the apparatus and a sample ejection head serving as a precisionpipette correspond to examples of the liquid ejection head. The liquidejection apparatus of the invention includes other industrial liquidejection apparatuses of industrial application.

1. A method of forging a metallic plate member, comprising steps of:providing a first die, in which a plurality of first projections arearranged in a first direction with a fixed pitch, each of the firstprojections being elongated in a second direction perpendicular to thefirst direction; providing a second die, in which a plurality of secondprojections are arranged in the first direction with the fixed pitch,each of the second projections being elongated in the second directionand provided with a concave portion extending in the second direction ata distal end portion thereof; providing a third die, in which a pair ofthird projections arranged in the second direction and elongated in thefirst direction so as to define a groove therebetween, each of the thirdprojections having a flat distal end face; opposing the first die to afirst face of the plate member while opposing the second die to a secondface of the plate member; performing a first forging work by sandwichingthe plate member with the first die and the second die in a thirddirection orthogonal to the first direction and the second direction, soas to generate a plastic flow of a material in the plate member intogaps defined between the first projections while generating a plasticflow of the material into the concave portion of each of the secondprojection; opposing the third die to the second face of the platemember, after the first forging work; and performing a second forgingwork, by sandwiching the plate member with the first die and the thirddie in the third direction, such that the flat distal end face of eachof the third projections generates a plastic flow of the material intothe gaps between the first projections, while a protrusion formed on theplate member by the concave portion is received by the groove, wherein aplurality of recesses formed by the first projections are partitioned bypartition walls formed by the material flown into the gaps between thefirst projections.
 2. A method of manufacturing a liquid ejection head,using the forging method as set forth in claim 1, the manufacturingmethod comprising steps of: forming a through hole in each of therecesses so as to communicate each of the recesses with the second faceof the plate member; joining a sealing plate onto the first face of theplate member so as to seal the recesses; providing a metallic nozzleplate formed with a plurality of nozzles; and joining the nozzle plate,with an adhesive agent, onto the second face of the plate member suchthat each of the nozzles is communicated with an associated one of therecesses via the through hole, wherein the liquid ejection head isconfigured such that liquid droplets are ejected from the nozzles bypressure fluctuation generated in liquid contained in the recesses. 3.The manufacturing method as set forth in claim 2, wherein a plurality ofdents formed by the second projections and remained on the second faceof the plate member are used to receive excess adhesive agent when thenozzle plate is joined onto the second face of the plate member.
 4. Themanufacturing method as set forth in claim 2, wherein a height of one ofthe flat distal end faces of the third projections which is closer to aportion where the through hole is to be formed is lower than the otherone of the flat distal end faces.